Comment by SG-
the 2.5Gbit USB network adapters using Realtek driver are actually bugged on macOS and only max out at 1.9Gbit/sec or so. Sadly the solution has been to use non-realtek 2.5Gbit adapters or simply get the 5Gbit Realtek ones that sell for almost the same price.
Are you sure? I just bought the Ugreen 2.5Gbps yesterday for this, and it uses a Realtek RTL8156BG chip. That’s the one I used to get way above 2Gbps straight to the UDR.